City officials said a hacker accessed the system and repeatedly sounded the sirens.
Officials say fire dispatch crews had to manually shut off the sirens. The city says they're trying to determine what caused the malfunction.
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To get to Memphis would require waiting until Saturday, and spending another night in Atlanta. Delta said those whose flights are cancelled and who don't travel are entitled to a refund.
The city can not say how the system was hacked, but it believes the hack was done within the Dallas area.
The hack is being investigated by system engineers and the Federal Communications Commission has been contacted, but police have not been involved, he said.
Surrounding cities also reported hearing sirens, but officials confirmed only the sirens in Dallas were triggered.
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An earlier version of this story was corrected to show that the system was completely shut off by 1:20 a.m. Saturday, not 1:20 p.m.
When it finally happens, the end of the world will likely begin like this: with wailing sirens tearing through the night sky sending chills down your spine as you contemplate if you've lived a good and meaningful life. They won't know the health of the sirens until the system is reactivated. The system is still down and the city is relying on other mass notification systems including reverse 911 and social media for emergencies.
Residents are asked to be patient and to avoid calling 911 or 311 as the sirens may sound again during reactivation.
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Dallas Mayor Mike Rawlings promised the perpetrator would be found and prosecuted. "Making the necessary improvements is imperative for the safety of our citizens".